System and Method for OFDMA Resource Management in WLAN

ABSTRACT

Embodiments are provided for implementing a control function in a Wireless Local Area Network (WLAN) for allocation of resources to multiple stations (STAs) to enable Orthogonal Frequency Division Multiple Access (OFDMA) communications. An embodiment method includes determining a plurality of transmission resources for OFDMA communications of a plurality of STAs in the WLAN. The determination includes allocating a plurality of subcarriers to the STAs. The method further includes signaling the determined transmission resources to the STAs. The signaling of the transmission resources is piggybacked on at least one of data and management frames, such as in a sub-header of a MAC frame, or is an explicit signaling, such as in one or more dedicated fields of a traffic specification information element. The transmission resources for OFDMA communications allow simultaneous transmissions of the STAs in the WLAN.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 14/299,797, filed on Jun. 9, 2014, which claims priority to U.S. Provisional Application No. 61/917,791, filed on Dec. 18, 2013, all which applications are hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to network communications, and, in particular embodiments, to a system and method for Orthogonal Frequency Division Multiple Access (OFDMA) resource management in Wireless Local Area Network (WLAN).

BACKGROUND

Wireless Local Area Networks (WLANs) commonly operate in unlicensed spectrum bands. Rules for operation in these bands force competing devices to share the available resources and defer their intended transmissions when the medium is sensed busy. Typically, a WLAN uses an Orthogonal Frequency Division Multiplexing (OFDM) transmission format in which all transmission resources are assigned to a single device. Random assignment is commonly achieved using carrier sense multiple access with collision avoidance (CSMA/CA). With CSMA/CA a device wins access to the medium, transmits its data up to a pre-defined period of time, and then gives up the medium for other devices to compete for transmission. In contrast, Orthogonal Frequency Division Multiple Access (OFDMA) is a transmission and access mechanism that accommodates multiple-user transmissions simultaneously. OFDMA is commonly implemented in wireless infrastructures operating in the licensed bands in order to meet timing information in terms of frame structure and the scheduling of resources among a subset of users. There is a need for efficient schemes for implementing OFDMA in WLANs.

SUMMARY OF THE INVENTION

In accordance with an embodiment, a method by a network component for managing orthogonal frequency-division multiple access (OFDMA) resources in a wireless local area network (WLAN) includes determining a plurality of transmission resources for OFDMA communications of a plurality of stations (STAs) in the WLAN. The determination includes allocating a plurality of subcarriers to the STAs. The method further includes signaling the determined transmission resources to the STAs. The transmission resources for OFDMA communications allow simultaneous transmissions of the STAs in the WLAN.

In accordance with another embodiment, a method for by a network component for managing OFDMA resources in a WLAN includes determining control parameters for establishing and synchronizing OFDMA communications for at least one of downlink and uplink transmissions between an access point (AP) and a plurality of STAs in the WLAN. The method further includes signaling the control parameters to the STAs.

In accordance with another embodiment, a network component for managing OFDMA resources in a WLAN comprises a processor and a computer readable storage medium storing programming for execution by the processor. The programming includes instructions to determine a plurality of transmission resources for OFDMA communications of a plurality of STAs in the WLAN. Determining the transmission resources includes at least one of allocating a plurality of subcarriers to the STAs. The network component is further configured to signal the determined transmission resources to the STAs, wherein the transmission resources for OFDMA communications allow simultaneous transmissions of the STAs in the WLAN.

In accordance with another embodiment, a method by a STA for OFDMA in a WLAN includes sending, to a network controller, information regarding at least one of scheduling transmissions for the STA, readiness of transmission, and preference of transmission. The method further includes receiving, from the network controller, a signaling of control parameters, which determine transmission resources for OFDMA communications of the STA. OFDMA communications are exchanged between the STA and an AP for at least one of downlink and uplink transmissions in accordance with the control parameters. The OFDMA communications exchanged between the STA and the AP are synchronized with one or more other STAs in accordance with the control parameters.

In accordance with yet another embodiment, a STA supporting OFDMA in a WLAN comprises a processor and a non-transitory computer readable storage medium storing programming for execution by the processor. The programming includes instructions to send, to a network controller, information regarding at least one of scheduling transmissions for the STA, readiness of transmission, and preference of transmission. The programming includes further instructions to receive, from the network controller, a signaling of control parameters, which determine transmission resources for OFDMA communications of the STA. The instructions further configure the STA to exchange, with an AP, OFDMA communications for at least one of downlink and uplink transmissions in accordance with the control parameters. The OFDMA communications exchanged between the STA and the AP are synchronized with one or more other STAs in accordance with the control parameters.

The foregoing has outlined rather broadly the features of an embodiment of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of embodiments of the invention will be described hereinafter, which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates a WLAN basic service set (BSS);

FIG. 2 illustrates an embodiment of WLAN control functions including a function for controlling OFDMA access;

FIG. 3 illustrates an embodiment of a OFDMA MAC sub-header for controlling OFDMA operations in a WLAN;

FIG. 4 illustrates a traffic specification (TSPEC) information element (IE) for carrying OFDMA control information in a WLAN;

FIG. 5 illustrates an embodiment of a method enabling OFDMA control in a WLAN; and

FIG. 6 is a diagram of a processing system that can be used to implement various embodiments.

Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.

Disclosed herein are system and method embodiments for implementing a control function in a WLAN for allocation of resources to multiple user devices, also referred to herein as stations (STAs), with OFDMA capability. The embodiments include using an OFDMA Coordination Function (OCF) for managing OFDMA resources in WLAN scenarios.

FIG. 1 shows an example of a WLAN basic service set (BSS) including an access point (AP) and one or more associated STAs. The AP is a communication device allowing the STAs to access and communicate using WLAN. The STAs are any user communication devices allowing users or subscribers to communicate with the AP and hence the WLAN. Examples of STAs include smartphones, tablet computers, laptop computers, desktop computers, sensor devices (e.g., smartwatch), and other mobile or communication devices with WLAN (e.g., WiFi) capability.

In general, an OFDMA system consists of N_(SC), subcarriers (N_(SC) is an integer) defined in a channel of certain bandwidth, W Megahertz (MHz). Each subcarrier represents a sub-range bandwidth or a frequency channel that can be used for uplink and/or downlink transmissions. For example in WLAN, the bandwidth W is usually set to 20 MHz. The subcarrier separation Δf is given by Δf=W/N_(SC). The OFDMA symbol duration T_(s) is given by 1/Δf. The quantity N_(SC) is set at 64 in WLAN OFDM implementation. With the introduction of OFDMA to WLAN, the number of subcarriers N_(SC) may be set to a higher value, such as 256 or 512 to support finer granularity. The number of subcarriers allocated to each user in a single transmission is one of the resource elements that is controlled or decided by the OCF.

FIG. 2 shows an embodiment of WLAN control functions including the OCF for controlling OFDMA access. A hybrid coordination function (HCF) controls both the controlled (scheduled) and the contention (random) access to the medium. A mesh coordination function (MCF) controls access (both controlled and contention) between neighboring mesh points (access points). The HCF provides a point coordination function (PCF), HCF controlled access (HCCA), and HCF/MCF contention access (EDCA). The MCF provides the EDCA and MCF controlled access. The OCF is a logical function that may reside either in a WLAN AP or in an access controller (AC). The AC is a server connected to the AP through an interface that allows the exchange of control information with the AP.

The OCF performs a number of functions that are needed for orderly operation of OFDMA in WLAN. The functions of the OCF include selection of users participating in every OFDMA transmissions, allocation of subcarriers to selected users, distribution of timing information (synchronization), and initiating uplink and downlink OFDMA transmission opportunities (TXOPs).

The OCF is also configured to signal and exchange information with the STAs for selection of STAs and allocation of subcarriers for the STAs. In an embodiment, the signaling information may be piggybacked on data and management frames. FIG. 3 shows an OFDMA MAC sub-header for controlling OFDMA operations in a WLAN. The OFDMA sub-header is part of a MAC frame and carries information about the OCF functions. The OFDMA sub-header can be a single bit in the data or management frames indicating to the OCF whether the user (STA) sending the frame has frames ready for transmission in its buffer. Alternatively, the OFDMA sub-header may include multiple sub-fields that may indicate parameters useful for the OCF to perform a more elaborate scheduling. These subfields may include bandwidth requirements, delay bounds, and/or other parameters relevant to the operation of the OCF. The OFDMA sub-header is also referred to as an OFDMA control field. The OFDMA sub-header can also be used to transfer OCF information from the OCF to the user. The OFDMA sub-header can also be defined as an OFDMA control field dedicated for this purpose.

In another embodiment, the communication between the OCF and the user can be done using explicit signaling (instead of the piggybacked signaling above). Explicit signaling can make use of signaling frames and information elements (IEs) that already exist in IEEE 802.11 specification, for example. FIG. 4 shows a Traffic Specification (TSPEC) IE that can be used for carrying OCF signaling from/to users (STAs), such as for exchanging traffic and reservation information between users and OCF. The information can be added to any suitable field group of fields of the IE shown in FIG. 4, depending on the size of the signaled information.

As described above, the functions of the OCF include allocation of subcarriers to selected users. In an embodiment, the OCF allocates subcarriers to users based on their traffic requirement. Further, the subcarriers may be assigned in groups that achieve some bandwidth granularity. The assignment of subcarriers in groups rather than a random fashion can simplify the designing of the overall OFDMA system.

The OFDMA is applicable both in uplink and downlink communications between the AP and the STA. A downlink OFDMA transmission starts when the AP competes and gains access to the wireless medium. Synchronization in the downlink direction is simpler than the uplink case since the AP and its related OCF can synchronize the multiple user transmissions using existing WLAN techniques and the physical layer (PHY) header information. On the other hand, synchronization at the start of an uplink OFDMA transmission opportunity (TXOP) is needed. The OCF is responsible for communicating synchronization information to users participating in the uplink OFDMA TXOP. The communication of the synchronization information can be in a special or dedicated frame that includes, for instance, clock information for each of the participating users. Timing information may take into account the distances between users and the AP as computed by the OCF.

FIG. 5 shows an embodiment of a method 500 enabling OFDMA control in a WLAN. The method 500 is performed by the OCF function, e.g., at the AP or at the AC. At step, 510, the OCF receives from the STA (via piggybacked or explicit signaling) information regarding readiness, scheduling, or preference of downlink/uplink transmissions. At step 520, the OCF determines control parameters for establishing and synchronizing OFDMA communication for downlink/uplink communications between the AP and one or more STAs. In addition to the information from the STAs, this consideration can use information such as available network resources (e.g., subcarriers and bandwidth), number of users (STAs), distance of users, and/or other relevant information for optimizing OFDMA and its resources. At step 530, the OCF signals the STAs information for controlling OFDMA transmissions in the WLAN. The signaling can be piggybacked, e.g., in an MAC subframe, or explicit, e.g., using an IE. The signaling can include information for designating the STAs participating in OFDMA transmissions, allocation of subcarriers to the participating STAs, distribution of timing information (synchronization) for the STAs, initiating uplink and downlink OFDMA transmission opportunities (TXOPs), or combinations thereof.

FIG. 6 is a block diagram of a processing system 600 that can be used to implement various embodiments. For instance the processing system 600 can be part of a AP, a STA, or an AC in a WLAN. Specific devices may utilize all of the components shown, or only a subset of the components, and levels of integration may vary from device to device. Furthermore, a device may contain multiple instances of a component, such as multiple processing units, processors, memories, transmitters, receivers, etc. The processing system 600 may comprise a processing unit 601 equipped with one or more input/output devices, such as a speaker, microphone, mouse, touchscreen, keypad, keyboard, printer, display, and the like. The processing unit 601 may include a central processing unit (CPU) 610, a memory 620, a mass storage device 630, a video adapter 640, and an I/O interface 660 connected to a bus. The bus may be one or more of any type of several bus architectures including a memory bus or memory controller, a peripheral bus, a video bus, or the like.

The CPU 610 may comprise any type of electronic data processor. The memory 620 may comprise any type of system memory such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), a combination thereof, or the like. In an embodiment, the memory 620 may include ROM for use at boot-up, and DRAM for program and data storage for use while executing programs. In embodiments, the memory 620 is non-transitory. The mass storage device 630 may comprise any type of storage device configured to store data, programs, and other information and to make the data, programs, and other information accessible via the bus. The mass storage device 630 may comprise, for example, one or more of a solid state drive, hard disk drive, a magnetic disk drive, an optical disk drive, or the like.

The video adapter 640 and the I/O interface 660 provide interfaces to couple external input and output devices to the processing unit. As illustrated, examples of input and output devices include a display 690 coupled to the video adapter 640 and any combination of mouse/keyboard/printer 670 coupled to the I/O interface 660. Other devices may be coupled to the processing unit 601, and additional or fewer interface cards may be utilized. For example, a serial interface card (not shown) may be used to provide a serial interface for a printer.

The processing unit 601 also includes one or more network interfaces 650, which may comprise wired links, such as an Ethernet cable or the like, and/or wireless links to access nodes or one or more networks 680. The network interface 650 allows the processing unit 601 to communicate with remote units via the networks 680. For example, the network interface 650 may provide wireless communication via one or more transmitters/transmit antennas and one or more receivers/receive antennas. In an embodiment, the processing unit 601 is coupled to a local-area network or a wide-area network for data processing and communications with remote devices, such as other processing units, the Internet, remote storage facilities, or the like.

While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein. 

What is claimed is:
 1. A method by an access point-side apparatus in a wireless local area network (WLAN), the method comprising: signaling transmission resources to one or more stations (STAs), the transmission resources allowing simultaneous orthogonal frequency-division multiple access (OFDMA) transmissions by the one or more STAs in the WLAN; the signaling being carried in an OFDMA sub-header of a Media Access Control (MAC) frame, and the OFDMA sub-header being dedicated as an OFDMA control field for carrying OFDMA control information to the STAs.
 2. The method of claim 1, wherein the MAC frame is a MAC data frame.
 3. The method of claim 1, wherein the signaling the transmission resources includes signaling a number of subcarriers allocated to each of the one or more STAs.
 4. The method of claim 1, further comprising: determining one or more transmission resources for OFDMA communications of the one or more STAs in the WLAN, wherein the determining includes allocating a plurality of subcarriers to the STAs; wherein the signaling the transmission resources to the one or more STAs comprises signaling the determined one or more transmission resources to the one or more STAs.
 5. The method of claim 4, wherein determining one or more transmission resources includes determining at least one of a number of subcarriers allocated to each one of the STAs for a single transmission, selecting the STAs participating for an occurrence of OFDMA transmissions, and allocating the subcarriers to the selected STAs.
 6. The method of claim 1, wherein the signaling the transmission resources is an explicit signaling for carrying OFDMA control information to the STAs.
 7. The method of claim 6, wherein the signaling is carried in one or more dedicated fields of a traffic specification information element.
 8. The method of claim 1, wherein the OFDMA sub-header includes a plurality of sub-fields for indicating communication parameters to the STAs.
 9. An apparatus for managing orthogonal frequency-division multiple access (OFDMA) resources in a wireless local area network (WLAN), the apparatus comprising: a processor; and a non-transitory computer-readable storage medium storing programming for execution by the processor, the programming including instructions to: signal transmission resources to one or more stations (STAs), the transmission resources allowing simultaneous orthogonal frequency-division multiple access (OFDMA) transmissions by the one or more STAs in the WLAN; the signaling being carried in an OFDMA sub-header of a Media Access Control (MAC) frame, and the OFDMA sub-header being dedicated as an OFDMA control field for carrying OFDMA control information to the STAs
 10. The apparatus of claim 9, wherein the MAC frame is a MAC data frame.
 11. The apparatus of claim 9, wherein the signaling the transmission resources includes signaling a number of subcarriers allocated to each of the one or more STAs.
 12. The apparatus of claim 9, the programming further including instructions to: determine one or more transmission resources for OFDMA communications of the one or more STAs in the WLAN, wherein the determining includes allocating a plurality of subcarriers to the STAs; wherein the signaling the transmission resources to the one or more STAs comprises signaling the determined one or more transmission resources to the one or more STAs.
 13. The apparatus of claim 12, wherein determining one or more transmission resources includes determining at least one of a number of subcarriers allocated to each one of the STAs for a single transmission, selecting the STAs participating for an occurrence of OFDMA transmissions, and allocating the subcarriers to the selected STAs.
 14. The apparatus of claim 9, wherein the signaling the transmission resources is an explicit signaling for carrying OFDMA control information to the STAs.
 15. The apparatus of claim 14, wherein the signaling is carried in one or more dedicated fields of a traffic specification information element.
 16. The apparatus of claim 9, wherein the OFDMA sub-header includes a plurality of sub-fields for indicating communication parameters to the STAs.
 17. A method by a station-side apparatus in a wireless local area network (WLAN), the method comprising: receiving, from an access point (AP), a Media Access Control (MAC) frame carrying signaling of transmission resources to one or more stations (STAs), the transmission resources allowing simultaneous orthogonal frequency-division multiple access (OFDMA) transmissions by the one or more STAs in the WLAN; the signaling being carried in an OFDMA sub-header of a Media Access Control (MAC) frame, and the OFDMA sub-header being dedicated as an OFDMA control field for carrying OFDMA control information to the STAs; and communicating with the AP using the transmission resources according to the signaling.
 18. The method of claim 17, wherein the MAC frame is a MAC data frame.
 19. The method of claim 17, wherein the signaling of the transmission resources includes signaling a number of subcarriers allocated to each of the one or more STAs.
 20. The method of claim 17, wherein the signaling of the transmission resources is an explicit signaling for carrying OFDMA control information to the STAs.
 21. The method of claim 20, wherein the signaling is carried in one or more dedicated fields of a traffic specification information element.
 22. The method of claim 17, wherein the OFDMA sub-header includes a plurality of sub-fields for indicating communication parameters to the STAs.
 23. A station-side apparatus supporting orthogonal frequency-division multiple access (OFDMA) in a wireless local area network (WLAN), the apparatus comprising: a processor; and a non-transitory computer-readable storage medium storing programming for execution by the processor, the programming including instructions to: process a Media Access Control (MAC) frame received from an access point (AP), the MAC frame carrying signaling of transmission resources to one or more stations (STAs), the transmission resources allowing simultaneous orthogonal frequency-division multiple access (OFDMA) transmissions by the one or more STAs in the WLAN; the signaling being carried in an OFDMA sub-header of a Media Access Control (MAC) frame, and the OFDMA sub-header being dedicated as an OFDMA control field for carrying OFDMA control information to the STAs; and communicate with the AP using the transmission resources according to the signaling.
 24. The apparatus of claim 23, wherein the MAC frame is a MAC data frame.
 25. The apparatus of claim 23, wherein the signaling of the transmission resources includes signaling a number of subcarriers allocated to each of the one or more STAs.
 26. The apparatus of claim 23, wherein the signaling of the transmission resources is an explicit signaling for carrying OFDMA control information to the STAs.
 27. The apparatus of claim 26, wherein the signaling is carried in one or more dedicated fields of a traffic specification information element.
 28. The apparatus of claim 23, wherein the OFDMA sub-header includes a plurality of sub-fields for indicating communication parameters to the STAs. 